Airports (in the United States) lacking a tower are sometimes served by a UNICOM radio. The UNICOM frequency gives pilots a common channel to communicate their intentions to other pilots in the vicinity of an uncontrolled airport.
It is generally required that pilots of aircraft having radio equipment permitting two-way communications should contact the Airport UNICOM to obtain advisory information and announce their intentions when within ten (10) miles of the Airport. Pilots are also encouraged to maintain a listening watch on the frequency when operating within a ten mile radius of the Airport. All departing aircraft shall announce on the UNICOM their intention and runway to be used for departure.
On initial contact, pilots report altitude, aircraft type and identification, and location relative to the airport and state their intention, to land or overfly.
Pilots give a status report on downwind, base and final approach.
FlightGear does not fully implement UNICOM entirely. UNICOM works best in multiplayer, where you actually have listeners.
- To access UNICOM, press the dash key (-) to enter the radio chat menu. Press the number that corresponds to '[XXX TRAFFIC]'
(where 'XXX' corresponds to the airport you are closest), then choose your message.
Air Traffic Control
See Air Traffic Control for the main article about this subject.
- ATC chatter (enable "Chatter" from the File > Sound Configuration dialog): plays random records of real ATC communications, probably best left disabled if going for multi-player mode with voice communications
- automatic ATIS generated from current METAR (tick the somewhat misleadingly named "ATC" sound configuration option): set COM1 to the ATIS frequency of the closest airport to hear a faint broadcast automatically generated by FlightGear—in a controlled multiplayer session and with FGCom turned on, you may hear a proper ATIS if it was recorded by the ATC, so always tune in first!
- FGCom (enable it from the multiplayer menu): for voice communications over the multiplayer network.
The Automatic Terminal Information Service is broadcast from most airports, informing about active runways, weather and conditions, exceptional airport information, etc. It is typically recorded every half-hour by controllers and looped over on a published frequency for pilots to listen before making contact.
Most radio racks have similar controls. As an example look at the Kx165 VHF communication transceiver and VHF navigation receiver.